1. Field of the Invention
The present invention generally relates to an apparatus and method for tuning the volume of sound downloaded from outside sources, and in particular, to an apparatus and method for tuning the volume of downloaded sound, in which, in a device for outputting downloaded sound through a speaker, the volume of the downloaded sound is tuned based on the stress ratio of the speaker.
2. Description of the Related Art
A mobile phone is a device that includes a speaker which may be used to output sound downloaded from an outside source. For example, a mobile phone can download a ring tone, a music file, a moving picture, or a game in a wired or wireless manner and outputs the downloaded ring tone through a speaker upon reception of a call, outputs the sound of the downloaded music file or moving picture through the speaker, or outputs the sound of the downloaded game when the downloaded game is played. A ring tone download function is representative of many multimedia functions of a mobile phone. The maximum volume of a ring tone is prescribed not to exceed a national standard level of 70 dBSPL. When a mobile phone is offered on sale on the market, sound sources that are previously loaded in the mobile phone and their volumes are adapted to such a standard. However, since the maximum volume of a ring tone downloaded by a user of a mobile phone is arbitrarily set by a service operator who provides a ring tone download service, the mobile phone cannot predict the volume of the downloaded ring tone. Thus, conventionally, after ring tones are downloaded from mobile phone manufactures, the user of the mobile phone selects one of the downloaded ring tones and determines the maximum volume of the selected ring tone as the maximum volumes of the total downloaded ring tones.
A factor that determines the maximum volume of a ring tone also includes the stress ratio of a speaker. This is because the output volume of a sound affects the life span of the speaker. The stress ratio of the speaker is a ratio of a root mean square of a voltage applied to the speaker to a rated voltage the speaker can tolerate. Generally, the stress ratio of the speaker is maintained constant for the life span of the speaker.
Since the maximum volume of unknown ring tones should be set to a representative value according to the volume of the ring tones and the stress ratio of the speaker, the volume of downloaded ring tones are generally lower than those of ring tones that are previously loaded in a mobile phone.
However, since the maximum volume of downloaded ring tones is set to a representative value, when many ring tones are downloaded, deviations among the volume of the downloaded ring tones are large. Such deviations range from 60 dBSPL to 70 dBSPL. Since a deviation of 10 dBSPL means a difference of 10 times in sound volume, deviations of 60-70 dBSPL indicate very large differences. Ring tones may be determined to be capable of being set higher after the stress ratio of a speaker is measured, but the maximum volume of downloaded ring tones is fixed to a specific value, resulting in degradation in efficiency.
Such a problem commonly occurs in not only a mobile phone but also in any device for outputting a sound including music downloaded from the outside through a speaker.